Nolan: Exactly. You exist now, and that you are sure of. Whether you will exist two seconds later is hardly relevant.
Robin S: Why existence is BEING. If you are, then you exist. If you can affect, then you exist. If something has changed a sliver because of your doing, then you exist.
You are sure that your mind exists. Nothing else is for sure. But this you are sure of; your existence is such that someone has decided to dupe you, with fake hands, fake feet, a fake universe. How could you dupe that which does not exist?
Therefore, if you think along the lines "Do I exist", then you have already proven to yourself that you do exist.
Now, we are straying from the topic.
I have already burned all my calendars, and have, since ten seconds ago, refused to believe in time-keeping.
I suggest you all follow suit.